Has THIS ever HAPPENED to you?
You have a nice three-pane Tableau line chart with multiple categories. It's a time-series. You want to adhere to (someone's version of) best design principles, so you choose to label each category on the right-hand end of the line. That's the most recent value, of course, and it's what you want to highlight.
You've already made some design choices to help highlight one particular category. You made that label and that line larger than the other categories.
So you create your chart, and wouldn't you know it? That automatically generated axis ends just a couple of ticks beyond your final value. That's not nearly enough room for your labels to sit pleasantly off to the right hand side.
They need space! Like a lion. They need space to live.
What to do? Well, the only thing you can do, really, aside from hand-typing in all the labels after the fact: you extend your horizontal axis manually.
Ah, that's better. Now at least you have room for your labels. But now there's all kinds of gunk on your screen. First of all, those axis values...they go out so far into the future! Your last data points are from 2017 and your axis goes all the way out to 2029. It's really kind of distracting. You can't programmatically get rid of them, but at least you can put your sheet on a dashboard and then float a text box over the offending years.
You also put some floating yellow vertical bars in between your panels to help separate them from each other.
Great. That's a couple of problems solved. But you also have a bunch of grid lines messing things up too! Meaningless crosshatches getting in the way of your labels. So you float a text box over those too.
Oh, geez. (You're Minnesotan in this scenario.) That just covers up the labels as well as the lines. But you don't want to turn off all your gridlines. And you also don't want to retype all you labels. What can you do?
You turn off your vertical gridlines, since those are the most annoying ones (they cut through your labels without even an excuse me!). Then, you create constant reference lines at every major axis tick, but ONLY up through the ones with data.
Now the only extraneous gridlines are the horizontal ones, and they aren't nearly as irritating.
Was it a few steps of extra work that aren't "necessary" for the final product? Sure. But it sure looks a lot nicer.
So remember, if you need to give your labels the space they need to live:
Extend the horizontal axis.
Cover up extraneous axis labels.
Turn off vertical gridlines and use constant reference lines instead.
Use column borders, floating elements, or whitespace to help define the boundaries between panes.